Histogram Equalization

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Description

Equalize the image histogram to a specified range and number of levels.

Usage

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equalize(x, range = c(0, 1), levels = 256)

Arguments

x

an Image object or an array

range

numeric vector of length 2, the output range of the equalized histogram

levels

number of grayscale levels (Grayscale images) or intensity levels of each channel (Color images)

Details

Histogram equalization is an adaptive image contrast adjustment method. It flattens the image histogram by performing linearization of the cumulative distribution function of pixel intensities.

Individual channels of Color images and frames of image stacks are equalized separately.

Value

An Image object or an array, containing the transformed version of x.

Author(s)

Andrzej Oles, andrzej.oles@embl.de, 2014

Examples

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  x = readImage(system.file('images', 'cells.tif', package='EBImage'))
  hist(x)
  y = equalize(x)
  hist(y)
  display(y, title='Equalized Grayscale Image')

  x = readImage(system.file('images', 'sample-color.png', package='EBImage'))
  hist(x)
  y = equalize(x)
  hist(y)
  display(y, title='Equalized Grayscale Image')